You're not going out with him/her, but you do like them, and they like you too. Basically you act like you're in a relationship and get jealous when they talk to the opposite gender.
(In Kelly's head): Danny is so cute!! Aww we would look so cute together!!
Danny: Hey Kelly.
Kelly: OMGOMG ARHAERIHgshroihERK HI DANNY!
Danny: You cute. I'ma talk to Cindy.
Danny: Hey cindy, you hot.
Kelly: WTFFFF WE'RE IN A CRUSHATIONSHIP!! YOU BROKE MY HEART!
Danny: *just ignores* So yeah Cindy, Prom 201_?
To take something small, that doesn't quite qualify as a theft. Probably from the Danish "skæv" or the Dutch "scheef", both of which are pronounced similarly, meaning "askew, or not quite right'. To change an item's ownership without permission, but only something small and of little worth.
"I skeefed an apple off the neighbor's tree." "I skeefed some chips outta your bag when you looked away." "Don't skeef my chair when I go to the bathroom."